RPM and MAP dropping

 Naveed wrote:

The Carburetors in the 914 do NOT have the Accelerator Pumps that your car used to.

The carb will stumble until the Air and Fuel Flow stabilize.

From page 7-10 of the Operators Manual:

As shown in the diagram, the throttle position at 108 to 110 % results in a rapid rise of nominal boost pressure. To avoid unstable boost, the throttle should be moved smoothly through this area either to full power (115 %) or, on a power reduction, to max. continuous power (100 %).

In this range (108 to 110 % throttle position) small changes in throttle position have a big effect on engine performance and speed, but are virtually not apparent for the pilot from the throttle lever position.

If I read the question carefully you are getting a drop in MP and RPM at full throttle. Then recovery? I have just had EFATO with same but worse symptoms got back with minimal throttle. Engine would only run at idle. Finally took fuel pressure regulator apart very simple device but found muck stuck on the O ring that was just letting the fuel recirculate, could not close to build up pressure to allow the main jets to operate.

Took fuel pressure regulator apart can be done with care only a diaphragm and spring with O ring to regulate pressure. Rubber is very fragile and I would definitely change regulator at 5 years with other rubber.